Top drives are used to suspend and rotate a drill string in drilling applications. The top drive is supported by a drilling line wrapped on a set of sieves and connected to drawworks at one extremity. The top drive supports the drill string via a thrust bearing. Mud may be pumped into the drill string via a swivel. Furthermore, the top drive generally includes one or more motors (e.g., electric or hydraulic motors) which generate(s) the rotation of the drill string. The reaction torque applied to the top drive may be transmitted to a mast via a set of rollers or slides attached to the top drive chassis.
In some situations, it may be useful to acquire data about the drilling process from within the drill string. However, the drill string may act as a shield against acquiring this data. In addition, because the drill string contains pressurized mud, it may be challenging to deploy data acquisition tools into the drill string. Furthermore, the drill string is rotating, which further complicates this task.